halfmoon betta

Decided to set up my old 14 gallon tank with a platinum halfmoon betta. Hopefully he enjoys the space. Here is a crappy phone video of him.

I have a koi halfmoon betta in a 2.5 gallon tank. I've had him for about 4 months now, and only recently moved him into this tank. Well for one the flow of the tank is pretty strong. Any suggestions on slowing the flow? The intake of the filter also seems to be pretty strong... I just turned it...